WO2011145346A1

WO2011145346A1 - Transmitting apparatus

Info

Publication number: WO2011145346A1
Application number: PCT/JP2011/002778
Authority: WO
Inventors: 裕二井口
Original assignee: 京セラ株式会社
Priority date: 2010-05-20
Filing date: 2011-05-18
Publication date: 2011-11-24
Also published as: JP2011244341A

Abstract

Disclosed is a transmitting apparatus (100), which amplifies input signals by means of amplifying sections (117, 118), and which transmits the signals from the signal output section (121). The transmitting apparatus is provided with: a signal input section (151) which inputs external feedback signals on the basis of output signals, which are outputted to an antenna (122) from an external connecting apparatus (123) connected to the signal output section (121); and correcting sections (111, 158), which correct the input signals on the basis of the external feedback signals inputted to the signal input section (151) such that the characteristics of the output signals from the external connecting apparatus (123) are compensated.

Description

Transmitter

Cross-reference of related applications

This application claims the priority of Japanese Patent Application No. 2010-116551 filed on May 20, 2010, the entire disclosure of which is incorporated herein by reference.

The present invention relates to a transmission device.

For example, a transmission device used in a base station of a wireless communication system is configured to output a transmission signal having a predetermined characteristic from its output terminal. As an example of such a transmission apparatus, for example, a transmission apparatus disclosed in Patent Document 1 is known. In the transmission apparatus disclosed in Patent Document 1, an input signal is used as a reference signal, and distortion is based on an error between the reference signal and a feedback signal extracted from a transmission signal supplied from an analog circuit unit including a power amplifier to an output terminal. A correction coefficient is calculated. Then, by multiplying the input signal by the calculated distortion correction coefficient and inputting it to the analog circuit unit, a distortion-compensated transmission signal is output from the output terminal.

JP 2003-188747 A

By the way, a base station of a wireless communication system is used to prevent interference with radio waves in adjacent frequency bands used by other wireless communication systems, or to use adjacent frequency bands during or after installation. In some cases, an external passive device such as a filter or a duplexer is connected to the output terminal of the transmission device in order to share the antenna with the base station. In addition, an external active device such as an amplifier may be connected to compensate for power loss due to connection of the external active device or power loss due to the feeder line.

However, as described above, the transmission device of the base station is configured to output a transmission signal having a predetermined characteristic from its output terminal. Therefore, when an external connection device such as an external active device or an external passive device is connected to the output terminal of the transmission device as described above, the transmission signal output from the external connection device deteriorates due to the characteristics of the external connection device. Therefore, there is a concern that communication quality may be degraded. Such a problem in the transmission apparatus occurs not only in the transmission apparatus of the base station but also in a transmission apparatus that outputs a transmission signal having a predetermined characteristic when connection of an external connection device is assumed.

Therefore, an object of the present invention is to provide a transmission apparatus that can solve such problems and can reduce deterioration of a transmission signal caused by an externally connected device.

An invention according to a first aspect for achieving the above object is a transmission device that amplifies an input signal by an amplification unit and transmits the amplified signal from a signal output unit
A signal input unit for inputting an external feedback signal based on an output signal output to the antenna from an external connection device connected to the signal output unit;
Based on the external feedback signal input to the signal input unit, a correction unit that corrects the input signal so as to compensate the characteristics of the output signal of the externally connected device;
It is characterized by providing.

The invention according to a second aspect is the transmission device according to the first aspect,
A compensation unit that receives an internal feedback signal based on a transmission signal supplied from the amplification unit to the signal output unit and corrects the input signal so as to compensate the characteristics of the transmission signal; To do.

The invention according to a third aspect is the transmission apparatus according to the second aspect,
A modulation unit that modulates the input signal and supplies the modulated signal to the amplification unit;
A demodulator that demodulates the external feedback signal or the internal feedback signal;
A selection unit that selectively inputs the external feedback signal or the internal feedback signal to the demodulation unit and supplies the demodulation signal to the corresponding correction unit or the compensation unit;
Is further provided.

The invention according to a fourth aspect is the transmitter according to the third aspect,
It further comprises a level adjusting unit that adjusts the level of at least one of the external feedback signal or the internal feedback signal that is selectively input to the demodulating unit.

According to the transmission device of the present invention, the input signal is corrected by the external feedback signal based on the output signal of the externally connected device, so that it is possible to reduce the deterioration of the transmitted signal by the externally connected device.

It is a functional block diagram which shows the structure of the transmitter which concerns on 1st Embodiment of this invention. It is a functional block diagram which shows the structure of the transmitter which concerns on 2nd Embodiment of this invention. It is a functional block diagram which shows the structure of the transmitter which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a transmitter incorporated in a base station of a wireless communication system represented by WiMAX (Worldwide Interoperability for Microwave Access) or LTE (Long Term Evolution) adopting an OFDM (Orthogonal Frequency Division Multiplexing) scheme Will be described as an example.

(First embodiment)
FIG. 1 is a functional block diagram showing the configuration of the transmission apparatus according to the first embodiment of the present invention. The transmission apparatus 100 includes a transmission system 110, an internal feedback system 130, and an external feedback system 150. The transmission system 110 includes an OFDM signal generation circuit 111, a digital distortion compensation circuit (DPD) 112, digital-analog conversion circuits (DAC) 113I and 113Q, low-pass filters (LPF) 114I and 114Q, and IQ modulation circuit (IQ-MOD) 115. A local oscillator (LO) 116, an amplifier (AMP) 117, a power amplifier (PA) 118, an isolator (ISO) 119, a duplexer (DUP) 120, and an antenna connection terminal 121. The antenna connection terminal 121 constitutes a signal output unit that outputs a signal output from the PA 118.

The internal feedback system 130 includes a directional coupler 131, a mixer (MIX) 132, an LO 133, an amplifier (AMP) 134, an IQ demodulation circuit (IQ-DEM) 135, LPFs 136I and 136Q, and an analog-digital conversion circuit (ADC) 137I. And 137Q. The external feedback system 150 includes an external input terminal 151, a MIX 152, an LO 153, an AMP 154, an IQ-DEM 155,

LPFs

156I and 156Q, ADCs 157I and 157Q, and an equalizer 158. The external input terminal 151 constitutes a signal input unit for inputting an external feedback signal.

In the transmission system 110, an OFDM signal generation circuit 111 receives an input data signal from an upper control station (not shown) or the like, and generates an in-phase component (I signal) and a quadrature component (Q signal) of the OFDM baseband signal. These I signal and Q signal are converted into analog signals by the

DACs

113I and 113Q via the DPD 112, then supplied to the IQ-MOD 115 via the

LPFs

114I and 114Q, and modulated by the radio frequency signal from the LO. The modulated signal modulated by IQ-MOD 115 is amplified by AMP 117, further amplified to a predetermined power by PA 118, and output as a transmission signal. This transmission signal is filtered by the DUP 120 via the ISO 119 and supplied to the antenna connection terminal 121. Therefore, AMP 117 and PA 118 constitute an amplification unit. The I signal and the Q signal generated by the OFDM signal generation circuit 111 are also supplied to the equalizer 158 of the external feedback system 150.

In the internal feedback system 130, the directional coupler 131 is provided in the transmission path between the ISO 119 and the DUP 120 of the transmission system 110, and a part of the transmission signal (transmission power) output from the PA 118 is used as an internal feedback signal. Distribute. The internal feedback signal distributed by the directional coupler 131 is supplied to the MIX 132, mixed with the signal from the LO 133, and converted to an intermediate frequency band. The frequency-converted internal feedback signal is amplified by the AMP 134 and then demodulated by the IQ-DEM 115 to generate analog I and Q signals. These analog I and Q signals are converted into digital signals by ADCs 137I and 137Q via LPFs 136I and 136Q, respectively, and fed back to DPD 112. Thereby, in the DPD 112, the I signal and the Q signal from the OFDM signal generation circuit 111 are corrected so as to compensate the characteristic (distortion) of the transmission signal caused by the nonlinearity of the PA 118. Therefore, the DPD 112 constitutes a compensation unit that compensates for the characteristics of the transmission signal output from the antenna connection terminal 121.

In the external feedback system 150, an external feedback signal based on the output signal of the external connection device connected to the antenna connection terminal 121 is input to the external input terminal 151. Similar to the internal feedback system 130, this external feedback signal is mixed with the signal from the LO 153 in the MIX 152, frequency-converted, amplified by the AMP 154, and demodulated into analog I and Q signals by the IQ-DEM 155. The The demodulated analog I and Q signals are converted into digital signals by ADCs 157I and 157Q via

LPFs

156I and 156Q, respectively.

The I signal and the Q signal converted into digital signals by the ADCs 157I and 157Q, respectively, are fed back to the equalizer 158. The equalizer 158 compares the fed back I signal and Q signal with the I signal and Q signal of the OFDM baseband signal from the OFDM signal generation circuit 111, and based on the comparison result, feeds back the I signal. And the deterioration of the frequency and phase of the Q signal is detected, correction information for correcting the deterioration is generated and supplied to the OFDM signal generation circuit 111.

As a result, the OFDM signal generation circuit 111 performs correction for each subcarrier so as to compensate for the characteristics of the output signal of the external connection device connected to the antenna connection terminal 121, and the I signal and the Q signal of the OFDM baseband signal. Is generated. Therefore, the OFDM signal generation circuit 111 and the equalizer 158 constitute a correction unit that corrects the input signal so as to compensate the characteristics of the output signal from the externally connected device. The reception signal input to the antenna connection terminal 121 is input to a reception system (not shown) via the DUP 120.

The transmission apparatus 100 according to the present embodiment is basically operated with the antenna 122 connected to the antenna connection terminal 121. However, for example, in order to prevent interference with radio waves in adjacent frequency bands used by other wireless communication systems, an external connection device is used between the antenna connection terminal 121 and the antenna 122 as shown in FIG. There is a case where a certain band pass filter (BPF) 123 is connected and operated. In this case, the transmission signal output from the antenna connection terminal 121 may deteriorate due to the characteristics of the BPF 123, and radio waves having desired characteristics may not be radiated from the antenna 122.

In such a case, a directional coupler 124 is provided in the transmission path between the BPF 123 and the antenna 122, whereby a part of the output signal of the BPF 123 is distributed as an external feedback signal, and the distributed external feedback signal is transmitted. This is supplied to the external input terminal 151 of the apparatus 100.

In this way, since the output signal of the BPF 123 is compensated by the OFDM signal generation circuit 111 based on the external feedback signal as described above, it is possible to radiate radio waves with desired characteristics from the antenna 122. It becomes. In addition, in this case, the output signal of the BPF 123 during operation of the transmission apparatus 100 can be monitored and compensated in real time, so that it is possible to cope with a change in the deterioration state due to an environmental change or a secular change. Thereby, it is possible to always radiate radio waves having desired characteristics from the antenna 122.

Note that, depending on the transmission device 100, an external connection device connected to the antenna connection terminal 121 of the transmission device 100 may be known from the installation environment of the base station. In such a case, prior to the actual operation of the transmission apparatus 100, the known external connection device is connected to the antenna connection terminal 121 of the transmission apparatus 100, and an arbitrary input signal from the transmission apparatus 100 is amplified. Output the transmission signal. Then, the output signal of the externally connected device at that time is appropriately attenuated and fed back to the external input terminal 151, whereby the correction information obtained from the equalizer 158 of the external feedback system 150 is, for example, Store in the equalizer 158.

Thereafter, in the actual operation of the transmission apparatus 100, feedback to the external input terminal 151 is stopped, and the correction information stored in the equalizer 158 is used by the OFDM signal generation circuit 111 as described above. An OFDM baseband signal is generated by correcting the input signal for each subcarrier. Thereby, the characteristic of the output signal of the known external connection apparatus connected to the antenna connection terminal 121 can be compensated. In this case, in an actual operation mode, it is not necessary to distribute a part of the output signal of the external connection device as an external feedback signal and feed it back to the external input terminal 151 of the transmission device 100. Therefore, there is no loss of transmission power for the feedback, and transmission power can be used effectively. In addition, since a directional coupler for obtaining an external feedback signal and a feeder line for supplying the distributed external feedback signal to the external input terminal 151 are not necessary, the cost can be reduced accordingly.

(Second Embodiment)
FIG. 2 is a functional block diagram showing a configuration of a transmission apparatus according to the second embodiment of the present invention. The transmission apparatus 200 includes a common feedback system 170 in which the internal feedback system 130 and the external feedback system 150 are shared in the configuration shown in FIG. The common feedback system 170 includes a directional coupler 171, an external input terminal 172, an input selection unit 173, MIX174, LO175, AMP176, IQ-DEM177, LPF178I and 178Q, ADC179I and 179Q, an output selection unit 180, and an equalizer 181. Prepare. Note that the configuration of the transmission system 110 and other externally connected devices is the same as that in FIG.

In the common feedback system 170, the directional coupler 171 is provided in the transmission path between the ISO 119 and the DUP 120 of the transmission system 110, as in FIG. 1, and is one of transmission signals (transmission power) output from the PA 118. Are distributed as internal feedback signals. The internal feedback signal is supplied to the input selection unit 173. In addition, as in FIG. 1, an external feedback signal based on an output signal of an external connection device connected to the antenna connection terminal 121 is input to the external input terminal 172. The external feedback signal is supplied to the input selection unit 173.

The input selection unit 173 switches and selects the internal feedback signal and the external feedback signal to be input at a predetermined timing and supplies them to the MIX 174. The feedback signal supplied to the MIX 174 is mixed with the signal from the LO 175 and converted to an intermediate frequency band, then amplified by the AMP 176 and demodulated by the IQ-DEM 177. As a result, analog I and Q signals are generated. These analog I and Q signals are converted into digital signals by ADCs 179I and 179Q via LPFs 178I and 178Q, respectively, and input to output selection section 180.

The output selection unit 180 feeds back the I signal and the Q signal from the ADCs 179I and 179Q to the DPD 112 or the equalizer 181 in synchronization with the input signal selection operation by the input selection unit 173. That is, when the internal feedback signal is selected by the input selection unit 173, the I signal and the Q signal from the ADCs 179I and 179Q corresponding to the internal feedback signal are fed back to the DPD 112. When an external feedback signal is selected by the input selection unit 173, the I signal and the Q signal from the ADCs 179I and 179Q corresponding to the external feedback signal are fed back to the equalizer 181. Therefore, the input selection unit 173 and the output selection unit 180 constitute a selection unit that selectively inputs an external feedback signal or an internal feedback signal and supplies the demodulated signal to a corresponding correction unit or compensation unit.

Note that the selection timing of the external feedback signal or the internal feedback signal by the input selection unit 173 and the output selection unit 180 can be set as appropriate. For example, in general, the internal feedback signal is selected and set to the compensation mode by the DPD 112, and the external feedback signal is selected for a predetermined time at an appropriate period to set the compensation mode by the equalizer 181 and the OFDM signal generation circuit 111. Here, the appropriate cycle is, for example, once to several times a day, several times a year, etc., or the cycle has a large amount of degradation depending on the signal degradation amount calculated based on the external feedback signal. In such a case, it can be shortened, or can be set appropriately for each maintenance of the base station.

In this way, by selectively performing distortion compensation of the transmission signal by the PA 118 and correction of deterioration of the output signal (transmission signal) by the BPF 123 which is an external connection device based on the internal feedback signal and the external feedback signal, Radio waves having desired characteristics can be radiated from the antenna 122. In addition, since the internal feedback signal and the external feedback signal are selectively processed by the common feedback system 170, the configuration of the transmission apparatus 200 can be simplified and the cost can be reduced.

(Third embodiment)
FIG. 3 is a functional block diagram showing the configuration of the transmission apparatus according to the third embodiment of the present invention. In the configuration shown in FIG. 2, the transmission device 300 includes an external feedback signal level adjustment unit 190 that is input to the IQ-DEM 177 of the common feedback system 170. Since other configurations are the same as those in FIG. 2, the same components are denoted by the same reference numerals, and description thereof is omitted.

The level adjustment unit 190 shown in FIG. 3 reduces the level of the external feedback signal, and includes a level detection circuit (DET) 191 and a variable attenuator (VATT) 192. An external feedback signal input to the external input terminal 172 is supplied to the DET 191 and the VATT 192. The DET 191 detects the level of the input external feedback signal, and controls the attenuation amount of the external feedback signal by the VATT 192 based on the detection result. As a result, in VATT 192, the level of the external feedback signal is attenuated to the same level as the level of the internal feedback signal from directional coupler 171 and is selectively supplied to IQ-DEM 177 via input selector 173. .

When the level of the external feedback signal input to the external input terminal 172 is assumed to be low, a variable gain amplifier circuit is provided in place of VATT 192, and the gain is controlled based on the detection level of the external feedback signal by DET 191. To do. As a result, the level of the external feedback signal selectively input to the IQ-DEM 177 is adjusted to the same level as the level of the internal feedback signal.

Thus, in transmission apparatus 300 according to the present embodiment, level adjustment section 190 adjusts the level of the external feedback signal input to IQ-DEM 177 to be approximately the same as the level of the internal feedback signal. As a result, the external feedback signal can be processed by appropriately setting the circuit constants of the common feedback system 170 so as to adapt to the level of the internal feedback signal that is normally processed. Therefore, each feedback control based on the internal feedback signal and the external feedback signal can be executed with higher accuracy.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications or changes can be made. For example, in FIG. 3, the level adjustment unit 190 may be provided to adjust the level of the internal feedback signal instead of adjusting the level of the external feedback signal. Further, the level adjustment unit 190 may be provided to adjust the levels of the internal feedback signal and the external feedback signal. In addition, the present invention is not limited to a transmission apparatus incorporated in a base station of a wireless communication system that employs an OFDM system, but a transmission apparatus that amplifies an analog or digital input signal and transmits it as an analog output signal, or a modulation or The present invention is widely applicable to a transmission device that transmits a predetermined beacon for modulation, a transmission device that does not have an internal feedback system, and the like.

100, 200, 300 Transmitter 110 Transmission system 111 OFDM signal generation circuit 112 Digital distortion compensation circuit (DPD)
115 IQ modulation circuit (IQ-MOD)
118 Power Amplifier (PA)
121 Antenna connection terminal 122 Antenna 123 Band pass filter (BPF)
130 Internal Feedback System 131 Directional Coupler 135 IQ Demodulator (IQ-DEM)
150 External feedback system 151 External input terminal 155 IQ-DEM
158 Equalizer 170 Common feedback system 171 Directional coupler 172 External input terminal 173 Input selection unit 177 IQ-DEM
180 Output Selection Unit 181 Equalizer 190 Level Adjustment Unit 191 Level Detection Circuit (DET)
192 Variable attenuator (VATT)

Claims

In a transmission device that amplifies an input signal by an amplification unit and transmits it from a signal output unit,
A signal input unit for inputting an external feedback signal based on an output signal output to the antenna from an external connection device connected to the signal output unit;
Based on the external feedback signal input to the signal input unit, a correction unit that corrects the input signal so as to compensate the characteristics of the output signal of the externally connected device;
A transmission device comprising:
A compensation unit that receives an internal feedback signal based on a transmission signal supplied from the amplification unit to the signal output unit and corrects the input signal so as to compensate the characteristics of the transmission signal; The transmission device according to claim 1.
A modulation unit that modulates the input signal and supplies the modulated signal to the amplification unit;
A demodulator that demodulates the external feedback signal or the internal feedback signal;
A selection unit that selectively inputs the external feedback signal or the internal feedback signal to the demodulation unit and supplies the demodulation signal to the corresponding correction unit or the compensation unit;
The transmission device according to claim 2, further comprising:
The transmission apparatus according to claim 3, further comprising a level adjustment unit that adjusts a level of at least one of the external feedback signal or the internal feedback signal that is selectively input to the demodulation unit.